Conventionally, a wiring substrate in which an electronic component is installed in a cavity of a first insulating layer via an adhesive layer is known. Such a wiring substrate includes, for example, a second insulating layer formed on the first insulating layer to cover the electronic component and a wiring pattern formed on an upper surface of the second insulating layer. The wiring pattern is electrically connected to a pad of the electronic component via a via hole formed in the second insulating layer. See, for example, Japanese Laid-open Patent Publication Nos. 2016-096292 and 2016-207958 for related art.